Incorrect type of implicitly typed const variables

[michaelneu]

The implicit type of const variables yields the initialization value of the variable:

main.ts

import { getInfoFromString } from "ts-type-info";

const code = `

var a = 10;
let b = 10;
const c = 10;

`;

const info = getInfoFromString(code);

for (const variable of info.variables) {
    console.log(`${variable.declarationType} ${variable.name}: ${variable.type.text};`);
}

Output with [email protected] and [email protected]

var a: number;
let b: number;
const c: 10;

This might be due to changes in the compiler API from TypeScript 2.0.10 to 2.1.1. npm install ts-type-info installed the latest version (2.1.4), which led to the output above. When uninstalling typescript, and manually installing 2.0.10, the output will look as follows:

Output with [email protected] and [email protected]

var a: number;
let b: number;
const c: number;

I don't know what this change might be yet, but if you want, I can take a look into it by the end of next week.

[dsherret]

This is new behaviour in TS 2.1 outlined here. You can also see the type of 10 if you hover over the variable name here (https://www.typescriptlang.org/play/#src=const%20c%20%3D%2010%3B).

On first glance, I'm going to say we should go with the change the typescript team made.

[michaelneu]

Thanks for your quick answer.

You're right, the choice of the typescript team seems logical, thus changing the behaviour here would be odd. Closing as "intended behaviour".